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INFECTION LEVELS OF TWO ASCARIDOID NEMATODES (ANISAKIS SIMPLEX AND PSEUDOTERRANOVA DECIPIENS) IN ATLANTIC COD
(GADUS MORHUA) OFF NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH CAP
by © Laura Carmanico
Thesis submitted to the School of Graduate Studies in partial fulfillment of the requirements for the degree of
Master of Science Department of Biology/ Faculty of Science Memorial University of Newfoundland
2018
St. John’s Newfoundland and Labrador
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ABSTRACT
Parasitic nematodes infecting the flesh of commercially important fish species pose an aesthetic and economic problem for the fishing industry. They also have potential health implications as they may cause disease in humans. The musculature of 811 Atlantic cod (Gadus morhua) from five cod stocks in the Northwest Atlantic off Newfoundland and Labrador, and on the Flemish Cap, were examined for two ascaridoid nematodes, Anisakis simplex sensu lato and Pseudoterranova decipiens sensu lato. I evaluated the distribution of these nematodes within the musculature of Atlantic cod, and investigated whether prevalence, abundance, or density varied among cod stocks or in relation to fish length. I used similar examination techniques to previous studies conducted during the 1940-50s and the 1980s, and compared infection levels to these studies. In all areas, prevalence and abundance of A. simplex s.l. increased substantially relative to historical studies. The highest infection levels of A. simplex s.l. were observed in fish from Northwest Atlantic Fisheries Organization (NAFO) Division 3M. The results are
consistent with a possible increase in abundance of some cetaceans, the definitive hosts of A. simplex s.l.; although population trends of most cetaceans are not well known. In most areas, infection levels of P. decipiens s.l. also increased since the 1980s. The area with the highest abundance of P. decipiens s.l. was the west coast of Newfoundland (Divisions 3Pn4R). Greater abundances could be related to an increase in abundance of grey seals (Halichoerus grypus) that serve as definitive hosts. Major changes in marine food webs following the collapse of groundfish stocks in the late 1980s and early 1990s, as well as
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increasing ocean temperatures, may also have influenced the population dynamics of these parasitic nematodes.
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ACKNOWLEDGEMENTS
First and foremost, I would like to thank my family for their tremendous support and patience throughout this process. I am also immensely thankful for the encouragement of friends throughout my studies which was invaluable to the completion of this work. I would also like to thank Bradley - I cannot express how grateful I am for his endless support and words of wisdom. This study would not have been possible without him.
My special thanks to those individuals at Centre for Fisheries Ecosystems Research, Fisheries and Oceans Canada, and the Fish, Food, and Allied Workers (FFAW) Union that assisted in the collection and processing of cod samples for this study. Particularly Wade Hiscock, Wade Murphy, Paul Higdon, Dwayne Pittman and Dan Porter. My supervisory committee members, Dr. Edward Miller and Dr. Garry Stenson offered insightful advice and comments on this thesis, for which I am very grateful. I would like to sincerely thank Dr. David Schneider and Dr. Noel Cadigan for their advice with the statistical component of this thesis. Dr. Christoph Konrad was also incredibly helpful in this aspect, and I’d like to thank him for his immense help and unwavering support.
This thesis would not have been possible without the guidance, help, and patience of my co-supervisor, Dr. John Brattey. His knowledge, endless support and kindness have been invaluable both academically and personally, and I cannot thank him enough. I would like to also thank my co-supervisor, Dr. Sherrylynn Rowe for supporting me throughout the process of completion and always providing encouragement. Her
assistance and thoughtful advice were very valuable, however I am particularly thankful
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for her caring and understanding nature. Financial support for this research was provided by grants to Dr. Sherrylynn Rowe from the Government of Newfoundland and Labrador through the Department of Fisheries and Aquaculture, the Research and Development Corporation (Ignite R&D), and the Department of Environment and Conservation (Institute for Biodiversity, Ecosystem Science, and Sustainability).
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Table of Contents
ABSTRACT ii
ACKNOWLEDGEMENTS iv
Table of Contents vi
List of Tables ix
List of Figures xv
List of Appendices xxi
1 General Introduction 1
1.1 Ecology and life cycle of A. simplex 2
1.2 Ecology and life cycle of P. decipiens 4
1.3 Factors influencing parasite abundance 6
1.4 Effects of parasites on fish hosts 8
1.5 Implications for human health 9
1.6 Technological solutions and preventative measures 9
1.7 Objectives 10
1.8 References 11
2 Infection levels of larval Anisakis simplex (Nematoda: Ascaridoidea) in the musculature of Atlantic cod (Gadus morhua) off Newfoundland and Labrador and on
the Flemish Cap 23
2.1 Abstract 23
2.2 Introduction 24
2.3 Materials and methods 28
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2.4 Statistical methods 30
2.5 Results 32
2.5.1 Summary of infection statistics by geographic region 32 2.5.2 Statistical modelling of prevalence and abundance data 33 2.5.3 Distribution within the musculature of Atlantic cod 38
2.5.4 Detection rate 39
2.5.5 Comparison with previous surveys 39
2.6 Discussion 42
2.7 References 49
3 Infection levels of larval Pseudoterranova decipiens (Nematoda: Ascaridoidea) in the musculature of Atlantic cod (Gadus morhua) off Newfoundland and Labrador and
on the Flemish Cap 86
3.1 Abstract 86
3.2 Introduction 87
3.3 Materials and methods 90
3.4 Statistical methods 93
3.5 Results 95
3.5.1 Summary of infection statistics by geographic region 95 3.5.2 Statistical modelling of prevalence and abundance data 97 3.5.3 Distribution within the musculature of Atlantic Cod 100
3.5.4 Detection rate 101
3.5.5 Comparison with previous surveys 102
3.6 Discussion 104
3.7 Bibliography 112
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4 General Discussion and Conclusion 148
4.1 References 154
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List of Tables
TABLE 2.1INFECTION STATISTICS FOR ANISAKIS SIMPLEX S.L. IN THE MUSCULATURE OF
ATLANTIC COD (GADUS MORHUA) SURROUNDING NEWFOUNDLAND AND LABRADOR,
AND THE FLEMISH CAP DURING 2012-2013.PREVALENCE: PERCENTAGE OF FISH INFECTED;ABUNDANCE: MEAN NUMBER OF NEMATODES PER FISH INCLUDING
UNINFECTED FISH (NEMATODES/FISH);MAXIMAL ABUNDANCE: MAXIMAL NUMBER OF NEMATODES IN A SINGLE FISH;MEAN DENSITY: MEAN NUMBER OF NEMATODES PER KILOGRAM OF MUSCULATURE (SKINNED NAPE AND FILLET) INCLUDING UNINFECTED FISH (NEMATODES/KG);MEAN INTENSITY: MEAN NUMBER OF NEMATODES IN INFECTED FISH EXCLUDING UNINFECTED FISH (NEMATODES/INFECTED FISH). ... 58 TABLE 2.2COMPARISON OF MODEL FITS FOR THE BINOMIAL DATA ON INFECTION (INFECTED
=1, NOT INFECTED =0) FOR ATLANTIC COD (GADUS MORHUA) SURROUNDING
NEWFOUNDLAND AND LABRADOR, AND THE FLEMISH CAP INFECTED WITH ANISAKIS SIMPLEX S.L. USING A LOGIT LINK FUNCTION AND BINOMIAL ERROR STRUCTURE.THE ASTERISK (*) INDICATES AN INTERACTION TERM IS INCLUDED AS A PARAMETER IN THE MODEL.THE MODEL OF BEST FIT IS INDICATED IN BOLD. ... 63 TABLE 2.3PARAMETER ESTIMATES FOR A GENERALIZED LINEAR MIXED-EFFECTS MODEL
[EQUATION 1] WITH BINOMIAL ERROR STRUCTURE AND LOGIT LINK FUNCTION FITTED TO BINOMIAL (PREVALENCE) DATA OF ANISAKIS SIMPLEX S.L. IN ATLANTIC COD (GADUS MORHUA) SURROUNDING NEWFOUNDLAND AND LABRADOR, AND THE FLEMISH CAP. VALUES IN PARENTHESES ARE STOCK ESTIMATES TRANSFORMED TO PROBABILITY OF INFECTION (I.E., PREVALENCE: PERCENTAGE OF FISH INFECTED). ... 64
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TABLE 2.4COMPARISON OF AIC VALUES TO DETERMINE BEST FITTING LINEAR MIXED-
EFFECTS MODEL FOR LOG(X+1)-TRANSFORMED COUNTS OF ANISAKIS SIMPLEX S.L. IN
ATLANTIC COD (GADUS MORHUA) SURROUNDING NEWFOUNDLAND AND LABRADOR,
AND THE FLEMISH CAP DURING 2012-2013.THE ASTERISK (*) INDICATES AN
INTERACTION TERM IS INCLUDED AS A PARAMETER IN THE MODEL.THE MODEL OF BEST FIT IS INDICATED IN BOLD. ... 65 TABLE 2.5PARAMETER ESTIMATES FOR A LINEAR MIXED-EFFECTS MODEL [EQUATION 2] OF
LOG(X+1)-TRANSFORMED COUNT DATA OF ANISAKIS SIMPLEX S.L. IN ATLANTIC COD
(GADUS MORHUA) SURROUNDING NEWFOUNDLAND AND LABRADOR, AND THE
FLEMISH CAP.VALUES IN PARENTHESES ARE STOCK ESTIMATES BACK-TRANSFORMED TO A LINEAR SCALE. ... 66 TABLE 2.6DISTRIBUTION OF LARVAL ANISAKIS SIMPLEX S.L. IN THE MUSCULATURE (LEFT
AND RIGHT NAPE AND FILLET) OF ATLANTIC COD (GADUS MORHUA) OFF
NEWFOUNDLAND AND LABRADOR AND ON THE FLEMISH CAP DURING 2012-2013.THE NULL HYPOTHESIS BEING TESTED WAS THAT NEMATODES ARE EQUALLY DISTRIBUTED BETWEEN LEFT AND RIGHT SIDES OF NAPE AND FILLET PORTIONS FOR FOUR LENGTH CLASSES OF COD. ... 67 TABLE 2.7PERCENTAGE OF ANISAKIS SIMPLEX S.L. RECOVERED FROM THE MUSCULATURE OF
ATLANTIC COD (GADUS MORHUA) SURROUNDING NEWFOUNDLAND AND LABRADOR,
AND THE FLEMISH CAP DURING 2012-2013 USING THE CANDLING AND SLICING TECHNIQUE.TOTAL: NUMBER OF NEMATODES RECOVERED CANDLING IN ADDITION TO THE NUMBER OF NEMATODES FOUND USING SUBSEQUENT HCL DIGESTION. ... 68
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TABLE 2.8SAMPLE SIZES, MEAN ABUNDANCE (VARIANCE), STANDARDIZED MEAN ABUNDANCE AND STANDARDIZED MEAN DENSITY (STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN ABUNDANCE OR DENSITY BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES) OF ANISAKIS SIMPLEX S.L. IN THE MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) SAMPLED FROM VARIOUS AREAS SURROUNDING NEWFOUNDLAND AND LABRADOR, AND THE FLEMISH CAP DURING
1985-1987(BRATTEY AND BISHOP 1992) AND 2012-2013.SAMPLING AREAS IDENTIFIED BELOW CORRESPOND TO THOSE IN FIGURE 1 OF BRATTEY AND BISHOP
(1992;APPENDIX B) AND REFERENCE NUMBERS CORRESPOND TO FIG.2.1. ... 69 TABLE 2.9SAMPLE SIZES, STANDARDIZED ABUNDANCE AND DENSITY (STANDARDIZED
NUMBERS WERE CALCULATED BY MULTIPLYING MEAN ABUNDANCE OR DENSITY BY
1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES) OF ANISAKIS SIMPLEX S.L. IN THE MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) SAMPLED FROM VARIOUS AREAS SURROUNDING NEWFOUNDLAND AND LABRADOR, AND THE FLEMISH
CAP DURING 1947-1953(TEMPLEMAN ET AL.1957),1985-1987(BRATTEY AND
BISHOP 1992) AND 2012-2013.SAMPLING AREAS IDENTIFIED BELOW CORRESPOND TO THOSE DESCRIBED IN FIGURE 11 AND TABLE IV OF TEMPLEMAN ET AL.(1957)
(APPENDICES C AND D), AND REFERENCE NUMBERS CORRESPOND TO FIG.2.2.THIS TABLE INCLUDES ONLY FISH ≥41 CM AND ONLY THE FILLETS (NAPES WERE
EXCLUDED).A=1947-1953,B=1985-1987,C=2012-2013. ... 77 TABLE 3.1INFECTION STATISTICS FOR PSEUDOTERRANOVA DECIPIENS S.L. IN THE
MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) OFF NEWFOUNDLAND AND
LABRADOR, AND ON THE FLEMISH CAP DURING 2012-2013.PREVALENCE:
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PERCENTAGE OF FISH INFECTED;ABUNDANCE: MEAN NUMBER OF NEMATODES PER FISH INCLUDING UNINFECTED FISH (NEMATODES/FISH);MAXIMAL ABUNDANCE:
MAXIMAL NUMBER OF NEMATODES IN A SINGLE FISH;MEAN DENSITY: MEAN NUMBER OF NEMATODES PER KILOGRAM OF MUSCULATURE (SKINNED NAPE AND FILLET)
INCLUDING UNINFECTED FISH (NEMATODES/KG);MEAN INTENSITY: MEAN NUMBER OF NEMATODES IN INFECTED FISH, EXCLUDING UNINFECTED FISH (NEMATODES/INFECTED FISH). ... 121 TABLE 3.2COMPARISON OF VARIOUS LINEAR MODEL FITS TO THE BINOMIAL DATA
(INFECTED =1, NOT INFECTED =0) FOR ATLANTIC COD (GADUS MORHUA)
SURROUNDING NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH CAP
INFECTED WITH PSEUDOTERRANOVA DECIPIENS S.L.MODELS WERE FITTED USING THE LOGIT LINK FUNCTION WITH A BINOMIAL ERROR STRUCTURE.THE ASTERISK (*)
INDICATES AN INTERACTION TERM IS INCLUDED AS A PARAMETER IN THE MODEL.THE MODEL OF BEST FIT IS INDICATED IN BOLD. ... 126 TABLE 3.3PARAMETER ESTIMATES FOR A GENERALIZED LINEAR MIXED-EFFECTS MODEL
[EQUATION 3] WITH BINOMIAL ERROR STRUCTURE AND LOG LINK FUNCTION FITTED TO BINOMIAL (PREVALENCE) DATA OF PSEUDOTERRANOVA DECIPIENS S.L. WITHIN
ATLANTIC COD (GADUS MORHUA) STOCKS SURROUNDING NEWFOUNDLAND AND
LABRADOR, AND ON THE FLEMISH CAP.VALUES IN PARENTHESES ARE STOCK EFFECT ESTIMATES TRANSFORMED TO PROBABILITY OF INFECTION (PREVALENCE). ... 127 TABLE 3.4COMPARISON OF VARIOUS LINEAR MODEL FITS TO THE LOG(X) TRANSFORMED
COUNT DATA WITHOUT UNINFECTED FISH (ZERO COUNTS) FOR ATLANTIC COD (GADUS MORHUA) SURROUNDING NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH
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CAP INFECTED WITH PSEUDOTERRANOVA DECIPIENS S.L.MODELS WERE FITTED USING THE IDENTITY LINK FUNCTION WITH A NORMAL ERROR STRUCTURE.THE ASTERISK (*)
INDICATES AN INTERACTION TERM IS INCLUDED AS A PARAMETER IN THE MODEL.THE MODEL OF BEST FIT IS INDICATED IN BOLD. ... 128 TABLE 3.5PARAMETER ESTIMATES FOR A LINEAR MIXED-EFFECTS MODEL OF LOG
TRANSFORMED COUNT DATA OF PSEUDOTERRANOVA DECIPIENS S.L. AFTER THE REMOVAL OF UNINFECTED FISH IN ATLANTIC COD (GADUS MORHUA) STOCKS SURROUNDING NEWFOUNDLAND AND LABRADOR.VALUES IN PARENTHESES ARE STOCK EFFECT ESTIMATES BACK TRANSFORMED TO A LINEAR SCALE.ALL FISH FROM STOCK 3M WERE REMOVED DUE TO THE SMALL SAMPLE SIZE (3 INFECTED FISH OUT OF A TOTAL 105). ... 129 TABLE 3.6DISTRIBUTION OF PSEUDOTERRANOVA DECIPIENS S.L. IN THE MUSCULATURE
(LEFT AND RIGHT NAPE AND FILLET) OF ATLANTIC COD (GADUS MORHUA) FROM STOCKS OFF NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH CAP DURING
2012-2013.THE NULL HYPOTHESIS BEING TESTED IS THAT NEMATODES ARE EQUALLY DISTRIBUTED BETWEEN LEFT AND RIGHT SIDES OF NAPE AND FILLET PORTIONS FOR FOUR LENGTH CLASSES OF COD. ... 130 TABLE 3.7PERCENTAGE OF PSEUDOTERRANOVA DECIPIENS S.L. RECOVERED FROM THE
MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) USING THE CANDLING AND SLICING TECHNIQUE.TOTAL: NUMBER OF NEMATODES RECOVERED CANDLING IN ADDITION TO THE NUMBER OF NEMATODES SUBSEQUENTLY FOUND USING HCL
DIGESTION. ... 132
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TABLE 3.8SAMPLE SIZES, MEAN ABUNDANCE (VARIANCE), STANDARDIZED MEAN ABUNDANCE AND STANDARDIZED MEAN DENSITY (STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN ABUNDANCE OR DENSITY BY 1/DETECTION RATE BASED ON RESPECTIVE DETECTION RATES) OF PSEUDOTERRANOVA DECIPIENS S.L.
IN THE FLESH OF ATLANTIC COD (GADUS MORHUA) FROM VARIOUS AREAS
SURROUNDING NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH CAP DURING
1985-1987(BRATTEY ET AL.1990) AND 2012-2013.SAMPLING AREAS CORRESPOND TO THOSE IN FIGURE 1 OF BRATTEY AND BISHOP (1992;APPENDIX B) AND REFERENCE NUMBERS CORRESPOND TO FIG.2.1. ... 133 TABLE 3.9SAMPLE SIZES, STANDARDIZED ABUNDANCE AND DENSITY (STANDARDIZED
NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN ABUNDANCE OR DENSITY BY 1/DETECTION RATE BASED ON RESPECTIVE DETECTION RATES) OF
PSEUDOTERRANOVA DECIPIENS S.L. IN THE MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) SAMPLED FROM VARIOUS AREAS SURROUNDING NEWFOUNDLAND AND
LABRADOR, AND ON THE FLEMISH CAP DURING 1947-1953(TEMPLEMAN ET AL.1957)
AND 2012-2013.SAMPLING AREAS IDENTIFIED BELOW CORRESPOND TO THOSE
DESCRIBED IN FIGURE 11 AND TABLE IV OF TEMPLEMAN ET AL.(1957;APPENDICES C
AND D), AND REFERENCE NUMBERS CORRESPOND TO FIG.2.2.THIS TABLE INCLUDES ONLY FISH ≥41 CM AND ONLY DATA FOR THE FILLETS (NAPES WERE EXCLUDED). .... 141
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List of Figures
FIGURE 1.1STUDY AREA INDICATING NAFODIVISION BOUNDARIES AND LOCATIONS WHERE ATLANTIC COD (GADUS MORHUA) WERE SAMPLED DURING 2012-2013.
NUMBERS WITHIN SHAPES CORRESPOND WITH THE SAMPLES THAT WERE GROUPED FOR COMPARISON WITH FIGURE 1 OF BRATTEY AND BISHOP (1992;APPENDIX B).1= SOUTHERN FUNK ISLAND BANK,2=NORTHEAST NEWFOUNDLAND SHELF,3=GRAND
BANK,4=SOUTHEAST SHOAL OF THE GRAND BANK,5=WHALE BANK,6=GREEN
BANK,7=SOUTHERN ST.PIERRE BANK,8=CAPE ST.MARY’S,9=PLACENTIA BAY, 10=PASS ISLAND,11=ROSE BLANCHE BANK,12=PORTLAND CREEK.EACH POINT INDICATES A SET WHERE MULTIPLE FISH WERE COLLECTED (APPENDIX A). ... 20 FIGURE 1.2A.THE VISCERA OF AN ATLANTIC COD (GADUS MORHUA) SHOWING ANISAKIS
SIMPLEX S.L. ENCYSTED IN THE LIVER, TWO NEMATODES CAN BE SEEN WITHIN THE CIRCLE.B.WITHIN THE CIRCLE IS AN ENCYSTED PSEUDOTERRANOVA DECIPIENS S.L. IN THE FLESH OF AN ATLANTIC COD.SCALES SEEN IN BOTH PHOTOGRAPHS ARE
APPROXIMATE. ... 21 FIGURE 1.3A.FILLET PORTION OF ATLANTIC COD (GADUS MORHUA) ON THE CANDLING
TABLE.B.THE SAME PORTION OF FILLET WITH THE CANDLING TABLE TURNED ON.THE ILLUMINATION CAUSES NEMATODES, INCLUDING ANISAKIS SIMPLEX S.L.(PICTURED ABOVE IN THE CIRCLE), TO APPEAR AS DARK SPOTS AND BECOME MORE EASILY
DETECTABLE.SCALES SEEN IN BOTH PHOTOGRAPHS ARE APPROXIMATE. ... 22 FIGURE 2.1STUDY AREA INDICATING NAFODIVISION BOUNDARIES AND LOCATIONS
WHERE ATLANTIC COD WERE SAMPLED DURING 2012-2013.NUMBERS AND POINTS SURROUNDED BY SHAPES INDICATE WHERE SAMPLES WERE GROUPED FOR THE
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COMPARISON OF NEMATODE INFECTION LEVELS CORRESPONDING TO FIGURE 1 OF
BRATTEY AND BISHOP (1992;APPENDIX B).1=SOUTHERN FUNK ISLAND BANK,2= NORTHEAST NEWFOUNDLAND SHELF,3=GRAND BANK,4=SOUTHEAST SHOAL OF THE GRAND BANK,5=WHALE BANK,6=GREEN BANK,7=SOUTHERN ST.PIERRE
BANK,8=CAPE ST.MARY’S,9=PLACENTIA BAY,10=PASS ISLAND,11=ROSE
BLANCHE BANK,12=PORTLAND CREEK.EACH POINT INDICATES A LOCATION WHERE MULTIPLE FISH WERE COLLECTED (APPENDIX A).ANY SAMPLES NOT ENCIRCLED WERE NOT USED IN THE COMPARISON TO HISTORICAL DATA FROM BRATTEY AND BISHOP
(1992). ... 79 FIGURE 2.2STUDY AREA INDICATING NAFODIVISION BOUNDARIES AND LOCATIONS
WHERE ATLANTIC COD WERE SAMPLED DURING 2012-2013.NUMBERS SURROUNDED BY SHAPES INDICATE WHERE SAMPLES WERE GROUPED FOR THE COMPARISON OF NEMATODE INFECTION LEVELS CORRESPONDING TO FIGURE 11 AND TABLE IV OF
TEMPLEMAN ET AL.(1957;APPENDICES C AND D).1=NORTHEAST COAST OF
NEWFOUNDLAND,2=NORTHERN GRAND BANK (WEST OF LONG 50°W),3=FLEMISH
CAP,4=SOUTHEAST GRAND BANK,5=SOUTHWEST GRAND BANK,6=ST.PIERRE
BANK (SOUTH OF LAT 46°30’N),7=CAPE ST.MARY’S TO PASS ISLAND,8=PASS
ISLAND TO CAPE RAY,9=SOUTH OF PORTLAND CREEK.EACH POINT INDICATES A LOCATION WHERE MULTIPLE FISH WERE COLLECTED (APPENDIX A).ANY SAMPLES NOT ENCIRCLED WERE NOT USED IN THE COMPARISON TO HISTORICAL DATA FROM
TEMPLEMAN ET AL.(1957). ... 80 FIGURE 2.3SCATTER PLOTS OF THE RELATIONSHIP BETWEEN NUMBER OF ANISAKIS SIMPLEX
S.L. PER FISH IN THE MUSCULATURE AND LENGTH (NEAREST CM) OF ATLANTIC COD
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(GADUS MORHUA) FROM FIVE COD STOCKS AROUND NEWFOUNDLAND AND LABRADOR AND THE FLEMISH CAP.SOLID LINE INDICATES THE PREDICTED NUMBER OF
NEMATODES FROM THE BEST FITTING LINEAR MIXED-EFFECTS MODEL, SEE TEXT FOR DETAILS.NOTE THE CHANGE IN THE Y-AXIS FOR DIVISION 3M. ... 81 FIGURE 2.4MEAN STANDARDIZED DENSITY (NUMBER OF NEMATODES/KG OF
MUSCULATURE) OF ANISAKIS SIMPLEX S.L. IN THE MUSCULATURE OF ATLANTIC COD SAMPLED FROM VARIOUS AREAS OFF NEWFOUNDLAND AND LABRADOR DURING 1985- 1987(BRATTEY AND BISHOP 1992) AND 2012-2013.STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN DENSITY BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES. ... 82 FIGURE 2.5 MEAN STANDARDIZED ABUNDANCE (NEMATODES/FISH) OF ANISAKIS SIMPLEX
S.L. IN THE MUSCULATURE OF ATLANTIC COD SAMPLED FROM VARIOUS AREAS OF
NEWFOUNDLAND AND LABRADOR DURING 1985-1987(BRATTEY AND BISHOP 1992)
AND 2012-2013.STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN ABUNDANCE BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES. ... 83 FIGURE 2.6MEAN STANDARDIZED ABUNDANCE (NEMATODES/FISH) OF ANISAKIS SIMPLEX
S.L. IN THE MUSCULATURE OF ATLANTIC COD SAMPLED FROM VARIOUS AREAS OFF
NEWFOUNDLAND AND LABRADOR, AND THE FLEMISH CAP DURING 1947-1953
(TEMPLEMAN ET AL.1957),1985-1987(BRATTEY AND BISHOP 1992) AND 2012-2013.
ONLY ATLANTIC COD ≥41 CM AND ONLY NEMATODES FOUND IN THE FILLETS (NOT THE NAPES) WERE INCLUDED IN THESE ANALYSES.1=NORTHEAST COAST OF
NEWFOUNDLAND,2=NORTHERN GRAND BANK (WEST OF LONG 50°W),3=FLEMISH
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CAP,4=SOUTHEAST GRAND BANK,5=SOUTHWEST GRAND BANK,6=ST.PIERRE
BANK (SOUTH OF LAT 46°30’N),7=CAPE ST.MARY’S TO PASS ISLAND,8=PASS
ISLAND TO CAPE RAY,9=SOUTH OF PORTLAND CREEK.WHERE BARS ARE MISSING,
THIS INDICATES THAT DATA WERE NOT COLLECTED IN THIS AREA FOR THE RESPECTIVE STUDY.STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN ABUNDANCE BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES. ... 84 FIGURE 3.1STUDY AREA INDICATING NAFODIVISION BOUNDARIES AND LOCATIONS
WHERE ATLANTIC COD (GADUS MORHUA) WERE SAMPLED DURING 2012-2013.
NUMBERS SURROUNDED BY SHAPES INDICATE WHERE SAMPLES WERE GROUPED FOR THE COMPARISON OF NEMATODE INFECTION LEVELS CORRESPONDING TO FIGURE 1 OF
BRATTEY ET AL.(1990;APPENDIX B).1=SOUTHERN FUNK ISLAND BANK,2= NORTHEAST NEWFOUNDLAND SHELF,3=GRAND BANK,4=SOUTHEAST SHOAL OF THE GRAND BANK,5=WHALE BANK,6=GREEN BANK,7=SOUTHERN ST.PIERRE
BANK,8=CAPE ST.MARY’S,9=PLACENTIA BAY,10=PASS ISLAND,11=ROSE
BLANCHE BANK,12=PORTLAND CREEK.EACH POINT INDICATES A LOCATION WHERE MULTIPLE FISH WERE COLLECTED (APPENDIX A).ANY SAMPLES NOT ENCIRCLED WERE NOT USED IN THE COMPARISON TO THESE HISTORICAL DATA FROM BRATTEY ET AL. (1990). ... 143 FIGURE 3.2STUDY AREA INDICATING NAFODIVISION BOUNDARIES AND LOCATIONS
WHERE ATLANTIC COD (GADUS MORHUA) WERE SAMPLED DURING 2012-2013.
NUMBERS SURROUNDED BY SHAPES INDICATE WHERE SAMPLES WERE GROUPED FOR THE COMPARISON OF NEMATODE INFECTION LEVELS CORRESPONDING TO FIGURE 11
AND TABLE IV OF TEMPLEMAN ET AL.(1957;APPENDICES C AND D).1=NORTHEAST
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COAST OF NEWFOUNDLAND,2=NORTHERN GRAND BANK (WEST OF LONG 50°W),3
=FLEMISH CAP,4=SOUTHEAST GRAND BANK,5=SOUTHWEST GRAND BANK,6= ST.PIERRE BANK (SOUTH OF LAT 46°30’N),7=CAPE ST.MARY’S TO PASS ISLAND,8
=PASS ISLAND TO CAPE RAY,9=SOUTH OF PORTLAND CREEK.EACH POINT INDICATES A SET WHERE MULTIPLE FISH WERE COLLECTED (APPENDIX A).ANY SAMPLES NOT ENCIRCLED WERE NOT USED IN THE COMPARISON TO THESE HISTORICAL DATA FROM TEMPLEMAN ET AL.(1957). ... 144 FIGURE 3.3MEAN STANDARDIZED DENSITY (NEMATODES/KG OF MUSCULATURE) OF
PSEUDOTERRANOVA DECIPIENS S.L. FOUND IN THE MUSCULATURE OF ATLANTIC COD
(GADUS MORHUA) FROM VARIOUS AREAS OFF NEWFOUNDLAND AND LABRADOR DURING 1985-1987(BRATTEY ET AL.1990) AND 2012-2013.NOTE THE CHANGE IN SCALE FOR EACH PANEL.STANDARDIZED NUMBERS WERE CALCULATED BY
MULTIPLYING THE MEAN DENSITY BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES. ... 145 FIGURE 3.4MEAN STANDARDIZED ABUNDANCE (NEMATODES/FISH) OF PSEUDOTERRANOVA
DECIPIENS S.L. IN THE MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) FROM VARIOUS AREAS OFF NEWFOUNDLAND AND LABRADOR DURING 1985-1987(BRATTEY ET AL.1990) AND 2012-2013.NOTE THE CHANGE IN SCALE FOR EACH PANEL.
STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN DENSITY BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES. ... 146 FIGURE 3.5MEAN STANDARDIZED ABUNDANCE (NEMATODES/FISH) OF PSEUDOTERRANOVA
DECIPIENS S.L. IN THE MUSCULATURE OF ATLANTIC COD (GADUS MORHUA) SAMPLED FROM VARIOUS AREAS OFF NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH
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CAP DURING 1947-1953(TEMPLEMAN ET AL.1957) AND 2012-2013.ONLY ATLANTIC COD ≥41 CM AND ONLY NEMATODES FOUND IN THE FILLETS (NOT THE NAPES) WERE INCLUDED IN THESE ANALYSES.1=NORTHEAST COAST OF NEWFOUNDLAND,2= NORTHERN GRAND BANK (WEST OF LONG 50°W),3=FLEMISH CAP,4=SOUTHEAST
GRAND BANK,5=SOUTHWEST GRAND BANK,6=ST.PIERRE BANK (SOUTH OF LAT
46°30’N),7=CAPE ST.MARY’S TO PASS ISLAND,8=PASS ISLAND TO CAPE RAY,9
=SOUTH OF PORTLAND CREEK.STANDARDIZED NUMBERS WERE CALCULATED BY MULTIPLYING THE MEAN DENSITY BY 1/DETECTION RATE, BASED ON RESPECTIVE DETECTION RATES. ... 147
xxi
List of Appendices
APPENDIX A.SAMPLING DETAILS FOR ATLANTIC COD (GADUS MORHUA) COLLECTED OFF
NEWFOUNDLAND AND LABRADOR, AND ON THE FLEMISH CAP DURING 2012-2013 AND EXAMINED FOR NEMATODES.B. REF INDICATES REFERENCE NUMBERS CORRESPONDING TO SAMPLING AREAS DESCRIBED IN FIGURE 1 OF BRATTEY AND BISHOP (1992) TO WHICH THAT SET WAS ASSIGNED (APPENDIX B).T. REF INDICATES REFERENCE NUMBERS CORRESPONDING TO SAMPLING AREAS DESCRIBED IN TABLE IV AND ILLUSTRATED IN FIGURE 11 OF TEMPLEMAN ET AL.(1957;APPENDICES C AND D) TO WHICH THAT SET WAS ASSIGNED. ... 158 APPENDIX B.FIGURE 1 EXTRACTED FROM BRATTEY AND BISHOP (1992) ILLUSTRATING
WHERE SAMPLES OF ATLANTIC COD (GADUS MORHUA) WERE COLLECTED.SAMPLING AREAS IN THE CURRENT STUDY WERE GROUPED AS CLOSELY AS POSSIBLE TO REGIONS DESCRIBED BELOW IN ORDER TO COMPARE INFECTION LEVELS OF ANISAKIS SIMPLEX S.L.
AND PSEUDOTERRANOVA DECIPIENS S.L.(APPENDIX A). ... 162 APPENDIX C.FIGURE 11 EXTRACTED FROM TEMPLEMAN ET AL.(1957) ILLUSTRATING
WHERE SAMPLES OF ATLANTIC COD (GADUS MORHUA) WERE COLLECTED.SAMPLING AREAS IN THE CURRENT STUDY WERE GROUPED AS CLOSELY AS POSSIBLE TO REGIONS DESCRIBED BELOW IN ORDER TO COMPARE INFECTION LEVELS OF ANISAKIS SIMPLEX S.L.
AND PSEUDOTERRANOVA DECIPIENS S.L.(APPENDIX A). ... 163 APPENDIX D.TABLE IV EXTRACTED FROM TEMPLEMAN ET AL.(1957) DESCRIBING
LOCALITIES ILLUSTRATED IN FIGURE 11(TEMPLEMAN ET AL.1957). ... 164
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1 General Introduction
Atlantic cod (Gadus morhua; referred to as “cod” in this thesis) is a demersal gadoid inhabiting the North Atlantic, primarily on continental shelfs. As a large predator at a high trophic level, it plays an important role in the ecosystem (Link et al. 2009). In the Northwest Atlantic around Newfoundland and Labrador, cod is managed as five separate stocks; the northern Labrador cod in Northwest Atlantic Fisheries Organization (NAFO) Divisions 2GH, the northern cod stock in Divisions 2J3KL, the southern Grand Bank stock in Divisions 3NO, the southern Newfoundland stock in Subdivision 3Ps, and the northern Gulf of St. Lawrence stock in Divisions 3Pn4RS. A fifth stock, the Flemish Cap stock in Division 3M, lies outside of Canadian waters (Fig. 1.1).
Cod have been harvested for centuries, and the fishery for this species was once the largest in Atlantic Canada (Scott and Scott 1988; Rose 2007). Following the collapse of many stocks in the late 1980s and early 1900s (Myers et al. 1996), many of the fisheries were placed under moratoria with the expectation that the populations would recover rapidly. Some fisheries have subsequently reopened although none have recovered to pre- moratorium levels.
A common problem when wild animals such as Atlantic cod are used for human consumption is the presence of parasites. They can occur in all wild animals and may be both unsightly and pathogenic to humans. Marine parasites are often generalists, capable of infecting multiple species of invertebrate, fish, and mammals (Marcogliese 2002).
Marine fish can serve either as definitive hosts (supporting the sexually reproducing life stage) or intermediate hosts (harbouring the parasite for at least part of its development;
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Marcogliese 2002). Many commercially exploited marine organisms can become infected with parasites which can be a problem for the seafood industry (McClelland 2002).
Atlantic cod serve as the definitive or intermediate host for many parasitic species (at least 107), most occurring in the viscera (Margolis and Arthur 1979; McDonald and Margolis 1995; Hemmingsen and MacKenzie 2001). The varied parasite fauna of Atlantic cod may be due in part to their generalist diet and wide distribution. This puts them in contact with many species of fish, invertebrates and other prey that may be host to numerous parasite species.
The fishing industry has expressed concern regarding the abundance of parasitic anasakid nematodes in the musculature of Atlantic cod. Nematodes in the flesh decrease the quality of fish products, are costly to remove, and are unappealing to consumers (Jenks et al. 1996; McClelland 2002). Many nematodes also pose a health concern as humans can become infected potentially resulting in zoonotic diseases. The parasites causing the most concern for the industry in Atlantic Canada, as well as being the most abundant in the flesh of cod, are two species complexes of ascaridoid nematodes,
Anisakis simplex sensu lato and Pseudoterranova decipiens sensu lato, commonly known as whale worm and seal worm, respectively (Fig. 1.2).
1.1 Ecology and life cycle of A. simplex
Anisakis simplex s.l. is a complex of species, with A. simplex sensu stricto being the primary species infecting marine fishes around Newfoundland and Labrador (Brattey and Bishop 1992; Mattiucci et al. 1997). This anisakid nematode has a broad distribution, infecting many species in most of the world’s oceans, and is commonly found in a
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number of commercially important marine fishes. In Atlantic Canada, hosts include Atlantic cod (Templeman et al. 1957; Chandra and Khan 1988; Brattey and Bishop 1992;
Boily and Marcogliese 1995; McClelland et al. 2011; Mehrdana et al. 2014), American plaice (Hippoglossoides platessoides; Boily and Marcogliese 1995), and pelagic fishes such as Atlantic herring (Clupea harengus; McGladdery 1986) and capelin (Mallotus villosus; Hays et al. 1998).
Anisakis simplex s.l. typically follows a pelagic life cycle where the definitive hosts are various marine mammals, primarily cetaceans, such as belugas (Delphinapterus leucas; Measures et al. 1995) and harbour porpoises (Phocoena phocoena; Ugland et al.
2004). Mature nematodes live in the stomach of the definitive host and release eggs that are expelled during defecation. The eggs become embryonated in seawater and sink to the sediment on the ocean floor where they moult within the egg before hatching into the third developmental stage (L3) larvae (Measures and Hong 1995; Køie et al. 1995;
Audicana and Kennedy 2008). Subsequently, L3 larvae consumed by small crustaceans are released from their cuticle and can encyst within these intermediate hosts (Køie et al.
1995). These obligate intermediate hosts (a host which the parasite must infect to undergo moulting, growth, or a morphological or developmental change) are preyed upon by numerous macroinvertebrates. This then allows A. simplex s.l. to become infective to fish species, including cod and herring, which serve as transport or paratenic hosts (where little or no development of the parasite occurs) and the L3s can be transferred to the definitive host during predator-prey interactions (Køie et al. 1995; Hays et al. 1998;
Klimpel et al. 2004). Records of cetacean diets off Newfoundland are limited and, although some cetaceans may prey on Atlantic cod, it has not been considered to be an
